We have developed a theoretical method of predicting the mass resolution for a quadrupole ion trap reflectron time-of-flight (QIT-reTOF) mass spectrometer as a function of the spatial and velocity distributions of ions, voltages applied to the electrodes, and dimensions of the instrument. The flight times of ions were calculated using theoretical equations derived with an assumption of uniform electric fields inside the QIT and with the analytical description of the potential including the monopole, dipole, and quadrupole components. The mass resolution was then estimated from the flight-time spread of the ions with finite spatial and velocity distributions inside the QIT. The feasibility of the theoretical method was confirmed by the reasonable agreement of the theoretical resolution with the experimental one measured by varying the extraction voltage of the QIT or the deceleration voltage of the reflectron. We found that the theoretical resolution estimated with the assumption of the uniform electric fields inside the QIT reproduced the experimental one better than that with the analytical description of the potential. The possible applications of this theoretical method include the optimization of the experimental parameters of a given QIT-reTOF mass spectrometer and the design of new instruments with higher mass resolution.

Progesterone is one of the steroid hormones. The hormone is especially important in preparing the uterus for the implantation of the blastocyst and in maintaining pregnancy. Its concentration in serum is measured to determine ovarian function and to predict early pregnancy. The progesterone concentration is also important for in-vitro fertilization and embryo-transfer outcomes. We have established isotope dilution liquid chromatography-tandem mass spectrometry as a primary method for the measurement of progesterone in human serum. Progesterone and its isotopic analogue, progesterone-(13)C(2), in serum were monitored at mass transitions of m/z 315.2/109.2 and 317.2/111.2 respectively in multiple-reaction monitoring (MRM) mode with electrospray positive ionization. For validation of the method, progesterone in a National Institute of Standards and Technology standard reference material (NIST SRM) was measured, and the measured results were in good agreement with the reference values within the uncertainty. On the basis of the established method, progesterone certified reference material (CRM) was developed in this work. The certified value was (1.41 ± 0.036) μg kg(-1). The repeatability of 1.1% and reproducibility of 0.14% showed that ID LC-MS-MS is a reliable and reproducible method. The expanded uncertainty for the measurement of progesterone in the CRM was approximately 2.6% within 95% confidence limits. The detection limit of progesterone was approximately 0.6 μg kg(-1). The progesterone CRMs were distributed to representative clinical laboratories in the Republic of Korea for comparison with the chemiluminescence immunoassay (CLIA), which is the most sensitive immunoassay method. The results from the comparison showed quite a large bias among the participating laboratories. This implies that the CRM is a very important material for establishment of traceability to its practical use.

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In this paper, we propose a transformation scheme used to analyze online gaming traffic properties and develop a traffic model. We analyze the packet size and the inter departure time distributions of a popular first‐person shooter game (Left 4 Dead) and a massively multiplayer online role‐playing game (World of Warcraft) in order to compare them to the existing scheme. Recent online gaming traffic is erratically distributed, so it is very difficult to analyze. Therefore, our research focuses on a transformation scheme to obtain new smooth patterns from a messy dataset. It extracts relatively heavy‐weighted density data and then transforms them into a corresponding dataset domain to obtain a simplified graph. We compare the analytical model histogram, the chi‐square statistic, and the quantile‐quantile plot of the proposed scheme to an existing scheme. The results show that the proposed scheme demonstrates a good fit in all parts. The chi‐square statistic of our scheme for the Left 4 Dead packet size distribution is less than one ninth of the existing one when dealing with erratic traffic.

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